I can say with no doubt, check your auto insurance, if they cover glass, go into the yard and find a big rock, now throw the rock at the windshield and break it like it never been broke, call insurance co and let them send one of those glass people to your house and they put a new windshield in. The hardest thing in the world to polish is glass, if clay cant bring it back nothing aggressive will. Mostly you will spin your wheels with alc or acetone. You can try some real boiling water wipes assuming it isnt cold of course, but it is easier to replace a windshield every decade then waste time and energy trying to repair them when they get oxidized.
Once it is beyond repair and you know you will replace, then I might be inclined to try a ceramic coating likje they do with lenses.